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From: Thomas Gleixner <tglx@linutronix.de>
To: Jeff Layton <jlayton@kernel.org>,
	John Stultz <jstultz@google.com>, Stephen Boyd <sboyd@kernel.org>
Cc: Vadim Fedorenko <vadim.fedorenko@linux.dev>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC] timekeeping: don't use seqcount loop in ktime_mono_to_any on 64-bit arch
Date: Tue, 10 Sep 2024 17:39:54 +0200	[thread overview]
Message-ID: <87ttena56d.ffs@tglx> (raw)
In-Reply-To: <ee39e467d23070c00aa39f12895fe346406f527f.camel@kernel.org>

On Tue, Sep 10 2024 at 08:32, Jeff Layton wrote:
> On Tue, 2024-09-10 at 13:58 +0200, Thomas Gleixner wrote:
>> > +#if BITS_PER_LONG == 64
>> > +ktime_t ktime_mono_to_any(ktime_t tmono, enum tk_offsets offs)
>> > +{
>> > +	ktime_t *offset = offsets[offs];
>> > +
>> > +	return ktime_add(tmono, READ_ONCE(*offset));
>> 
>> Where is the corresponing WRITE_ONCE()?
>> 
> I'll just make it do a simple fetch without READ_ONCE.

Which will make KCSAN complain ...

So yes, READ_ONCE() is the correct thing todo, but then we want to have
the counterpart at the write sides.

Thanks,

        tglx

      reply	other threads:[~2024-09-10 15:39 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-09-10 11:17 [PATCH RFC] timekeeping: don't use seqcount loop in ktime_mono_to_any on 64-bit arch Jeff Layton
2024-09-10 11:58 ` Thomas Gleixner
2024-09-10 12:32   ` Jeff Layton
2024-09-10 15:39     ` Thomas Gleixner [this message]

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